Diffusion and reactions of oxygen during ageing for conventionally cured natural rubber vulcanisate

At high temperatures, oxidative ageing affects only the rubber near the surface, as essentially all the oxygen is consumed by reaction with antioxidant or rubber before it can diffuse into the bulk. A resinous oxidized layer is formed and in the center of large components is essentially anaerobic. The inhomogeneous natures of ageing for a large rubber component were carried out utilizing thickness effect measurements. The effect of ageing at different distances from the surface was studied using volume swelling measurements. Based on diffusion and chemical reactions theory, an estimation of the oxidized layer formation during ageing can be calculated provided the reaction rate is constant and the diffusion coefficient for given ageing temperature is known. For this purpose, oxygen uptake measurements were carried out in pure oxygen at 100 degrees C.